You should enjoy your maternity leave, people keep telling me, and funnily enough I am. Maybe it really did take a fifth child and a looming menopause to make it fun to have a baby. It's harder work, as lugging her around gives me terrible backache, but it's a joy. As I don't want my other children to read this and start asking me why I didn't enjoy them, let me be clear that I did, I really did. It's just that this baby feels more shared. Motherhood can be a lonely business, which is why we all huddle together at baby swimming classes or toddler singing sessions.

"The swimming is lovely," a mother I meet tells me. "Afterwards we sit around and chat over coffee. Although you can't help comparing your baby's development with the other babies. It's a bit competitive."

It's really only other mothers and close family who will listen to the sort of detail you want to provide, about how your baby is sleeping, feeding and pooing. Some fathers engage in these babyhood issues but more in a problem-solving way. First time round I could spend at least an hour on any one of those specialist subjects. Now when people ask me how Flora is sleeping I'd still like to discuss it fully but notice when their eyes glaze over.

But with Lydia, Tilly and Maddy (Sam isn't living at home although he still keeps his dirty clothes in his room) there are more people involved in this baby. Tilly asks me every morning how Flora slept. If Flora grizzles they all try to distract her, and in doing so distract me. Unlike my previous babies, I don't need to take this one with me every time I go to the toilet. One of the girls will take her. I can drink cups of tea, get dressed – anything that's a unit of five minutes. It is only during non-school hours, but it dilutes the feeling I've always had with a baby that I'm ever so slightly trapped.

After most of my babies I scurried back to work out of economic necessity. That's not to say I'm flush now, just older and in a lifetime of paying the mortgage, I'll take a bit longer. This time I know, will never, except in the most freakish of circumstances, come again. So this longer than usual maternity leave is also meant to be of some benefit to Tilly, 11, and Lydia, nine. With the arrogance of motherhood I assume they would like me to be around more. I tell Lydia that I may take a month off over the summer because it's ridiculous to go back to work just as they start their holidays. "But I won't be paid so we won't have much money. We can still have fun."

I wait for her to shout yippee. Lydia thinks for a minute. "You'd better go back to work," she says. "We need money." But I have never had a summer off with my children, and like it or not, they are going to have to put up with me. I daydream about how I can go to school assemblies and sports days without rushing into work late or leaving early. I already have morning coffees with the school mothers. Maybe they'd like to see more of me as well and we could go on day trips together.

I enjoy picking the children up every day from school. "Isn't it great that I can pick you up?" I ask.

"Only when you bring us sweets," says Lydia.

One afternoon I arrive at school early and wander around with Flora, proud I've managed to find a top without posset on it, chatting to the other mums.

Then K, who has children in the same class as mine, beckons me over.

"I had to tell you: you've got some food stuck round your mouth."

"But I've been talking to lots of people. I'm so embarrassed," I bleat.